Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local post-foothold EoP: AV:L and PR:L because a low-privileged local session is required, AC:L for reliable triggering, and C/I/A:H reflecting SYSTEM-level total impact.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
5DescriptionNVD
Use after free in Windows Installer allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Windows Installer (MSI) service affects a broad range of Windows client and server releases, from Windows 10 1607 and Server 2012 through Windows 11 25H2/26H1 and Server 2025. A use-after-free (CWE-416) in the Windows Installer component lets a low-privileged authenticated attacker who already has local code execution corrupt memory to run code with elevated (SYSTEM-level) privileges. No public exploit identified at time of analysis and the SSVC exploitation status is 'none', but the technical impact is rated total and Microsoft has shipped a patch.
Technical ContextAI
The affected component is the Windows Installer (msiexec/msi service), the OS subsystem responsible for installing, repairing, and removing MSI packages, which frequently runs installation actions in an elevated SYSTEM context. The root cause is a use-after-free (CWE-416): a memory object is freed and then referenced again, allowing an attacker to reclaim the freed allocation with attacker-controlled data and manipulate execution flow or write primitives. Because Windows Installer routinely elevates to perform system-level operations, a memory-corruption bug in this trusted service is a classic vehicle for turning a normal user context into SYSTEM. The CPE and EUVD data confirm this spans the shared Windows codebase across Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025, including Server Core installations.
RemediationAI
Apply the Microsoft security update for CVE-2026-50490 via the standard monthly cumulative/rollup update for your OS build; the fix is delivered by reaching or exceeding the patched build for your version, for example 10.0.19045.7548 (Windows 10 22H2), 10.0.26100.8875 (Windows 11 24H2), 10.0.26200.8875 (25H2), 10.0.28000.2269 (26H1), 10.0.20348.5386 (Server 2022), 10.0.26100.33158 (Server 2025), 6.2.9200.26226 (Server 2012), and 6.3.9600.23291 (Server 2012 R2). Consult the MSRC update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50490 for the exact KB per platform. There is no vendor-published workaround for the code flaw itself; because exploitation requires an existing local low-privilege session, meaningful compensating controls until patching are to restrict interactive and remote-shell logon rights to untrusted users, enforce least privilege and application allowlisting to reduce arbitrary local code execution, and monitor for anomalous msiexec/Windows Installer activity - with the trade-off that these reduce but do not eliminate the escalation path and may affect legitimate software installation workflows. Note Windows Server 2012/2012 R2 are outside mainstream support, so patching may require Extended Security Updates.
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Same weakness CWE-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-44104
GHSA-p83h-w63g-r43h